Inkjet cartridges are typically sealed with adhesive tape over the ink orifices to prevent ink evaporation, ink leakage, and contamination from getting into the nozzle holes. The adhesive of the adhesive tape tends to swell and soften when in contact with ink. The swollen softer adhesive can and does flow into the nozzle holes of the ink cartridge and occludes them, thereby preventing ejection of ink from the print head. This represents a challenge to engineer an adequate solution for both sealing the nozzle holes and not occluding them. All pressure sensitive adhesive based adhesive systems are reasonably expected to suffer from this same defect.
Most manufacturers have addressed this problem primarily through two approaches. First is to use a thermoplastic adhesive that has adherent properties when hot, and plastic properties when cool. The thermoplastic is heated just long enough to adhere the film to the nozzle plate and seal the nozzle holes; the thermoplastic promptly cools, freezing the material in place. In this form thermoplastic adhesives are significantly less susceptible to swelling, softening and flowing upon contact with ink. The second method involves a mechanical seal. A mechanical seal is usually composed of an elastomeric component that can be physically squeezed against the nozzle plate surface to seal the nozzle holes. Several variations of these are known in the art.
One known variation is to apply a tape having an uncured layer on the surface facing the nozzles. The uncured layer then is cured in a pattern which surrounds each nozzle. Curing may be by ultraviolet light or electron beam.
Other known options are to use a separate cap of some kind instead of a tape or the like directly over the orifices. Such options are prone to ink leakage because of poor sealing, with consequent ink migration over the printhead. This is unacceptable to the customer.
U.S. Pat. No. 6,634,732 B2 to Farr et al. is generally illustrative of the sealing of inkjet orifices of a cartridge a with a tape member. This invention is directed to the sealing of orifices of such cartridges.
With ongoing progress in inkjet printing, the nozzle holes are smaller. Smaller holes are more subject to being clogged. Direct application of tape on the nozzles entails some entry of tape material into the nozzle orifices, such as by initial pressure or by creep over time because of heat or chemical action of the ink. In the small orifices especially, the entered material is prone to breaking off and clogging the orifice.
Conventional pressure sensitive adhesive now used to seal nozzle holes is mobile and has a melting point significantly less than 400 degrees C. The mobility of pressure sensitive adhesive is necessary for the adhesive to closely conform to the surface to which it is applied and thereby adhere to it. Heat may be applied along with pressure when nozzles are sealed with pressure sensitive adhesive. But temperatures are limited as ink near the nozzles can expand and be expelled by high heat. Ink on the nozzle plate tends to destroy the sealing action of pressure sensitive adhesive.
Of course, any such seal must be removed for use of the ink cartridge. This invention recognizes that the system must have characteristics which permit the seal to be removed under moderate pressure by a human hand or finger.